Year: 2023
Type: article
Abstract: Krische and co-workers from the University of Texas reported an unusual deoxygenative cine substitution of vinyl triflates mediated by a dinuclear iodide-bridged palladium(I) complex (J.Am.Chem.Soc., DOI: 10.1021/jacs.3c09876).Traditionally, vinyl triflates react with palladium(0) complexes in an oxidative addition process that results in ipso substitution following transmetalation with a suitable electrophile and reductive elimination.The authors discovered that a dinuclear iodide-bridged palladium(I) complex, formed from Pd(OAc) 2 and Bu 4 N + I -in the presence of sodium formate as a reductant, undergoes a Heck-type reaction whereby carbopalladation occurs with concomitant elimination of triflate to form a palladium(IV) carbene.Reductive elimination gives the cinecoupling product and regenerates palladium(II), which undergoes reduction with formate to reform the bridged palladium-(I) complex and achieve catalyst turnover.The reaction utilizes aryl iodides as the cross-coupling partners, with the scope somewhat limited to electron-rich arenes.Ethers, esters, phenols, and carboxaldehydes are all tolerated under the reaction conditions.N-substituted pyrazole and N-H indole were also demonstrated as cross-coupling partners.The demonstrated scope of vinyl triflates is currently limited to cyclic examples, but potentially sensitive functionalities including silyl ethers, ketals, and carbamates were all tolerated. ■ ASYMMETRIC SYNTHESIS OF α-TRISUBSTITUTED α-TERTIARY AMINESSchlegel, Nguyen, and co-workers from Wayne State University reported the asymmetric synthesis of α-trisubstituted α-tertiary amines catalyzed by rhodium through a dynamic kinetic asymmetric transformation (DYKAT) (J.Am.Chem.Soc., DOI: 10.1021/jacs.3c04211).The controlled synthesis of α-trisubstituted α-tertiary amines has remained elusive until now because of the challenges in controlling the selectivity of highly substituted C-N bond formation.Such amine products contain five distinct substituents, giving significant opportunity to explore chemical space if the products can be accessed in a selective fashion.The authors found that the combination of a rhodium catalyst and a chiral diene ligand was able to achieve high selectivity for the formation of α-trisubstituted α-tertiary amines from racemic tertiary allylic trichloroacetimidates and secondary amine nucleophiles.Mechanistic investigations showed that enantiodifferentiation occurs prior to attack by the amine nucleophile on the enantiomeric π-allyl complex, with the allylic electrophile remaining racemic throughout the progression of the reaction.It was also shown that the reaction is nonreversible
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4389367580